Economic action to stop global warming

The chart below explains each of the Princeton University Carbon Mitigation Initiative's (CMI) strategies for reducing carbon dioxide emissions by one billion tons per year. (Learn more about Scale of the Climate Crisis and CMI's strategies.) We need to implement at least seven of these strategies now to avoid the worst environmental consequences of climate change.

Strategies endorsed by Green America appear in green, strategies we endorse with reservations are in brown, and strategies we do not endorse are in red.

Princeton's CMI Recommendations

Green America's Take

1. MORE EFFICIENT VEHICLES. Increase the fuel economy for 2 billion cars from 30 to 60 mpg by 2054.

This is a necessary step as we work toward developing zero-emission vehicles. Today, we can all purchase cars that are close to this goal by choosing either a Honda Insight or Toyota Prius hybrid, or by driving a car powered by
100-percent biodiesel.

2. REDUCE OUR USE OF VEHICLES.
Decrease car travel for 2 billion 30-mpg cars from 10,000 to 5,000 miles per year through 2054, in part through better urban design, increased use of mass transit, and telecommuting.

We endorse this step, including designing communities to facilitate increased walking and biking.

3. MORE EFFICIENT BUILDINGS. Cut carbon emissions by one-fourth in buildings and appliances projected through 2054.

We endorse this step as we work toward zero-emission buildings and appliances.

4. REDUCED DEFORESTATION, PLUS REFORESTATION, AND
NEW PLANTATIONS. Decrease tropical deforestation to zero instead of 0.5 GtC/year, and establish 300
Mha of new tree plantations (twice the current rate).

In the short-term, all coal plants should operate at 60 percent efficiency, or shut them down. Starting immediately, no new coal plants should be built, due to the social and environmental problems associated with coal mining and pollution from dirty coal plants. Put more resources into developing cleaner energy alternatives to replace coal entirely in the future.

Natural gas is a fossil fuel, so its extraction is resource-intensive
and its supply is finite. We endorse this step as a short term strategy while zero-emissions renewable technologies that
can replace natural gas are put into place.

No new coal plants should be built starting today. CCS is a technology that allows carbon from coal plants to be turned into a gas and stored underground. CCS may be a viable strategy for existing coal plants in the short term, but there are concerns surrounding the safety of storing carbon
underground, as well as concerns that the CO2 stored underground would eventually be released into the atmosphere. There are also doubts as to whether CCS technology can be ready at the CMI-recommended scale in ten years. CCS should be added to existing coal plants.

11. WIND-GENERATED HYDROGEN IN FUEL-CELL CARS FOR GASOLINE IN HYBRID CARS. Add 4 million 1-megawatt-peak windmills (100 times the current capacity).

Zero-emission transportation is a must, so we endorse the direction suggested here, but not the specifics. While this
CMI wedge calls for fuel cells powered by wind-generated hydrogen* (H2), it would be better to not create a H2
infrastructure. Developing plug-in hybrids now and all electric vehicles powered by renewables is more energy-efficient and cost-effective overall. (See #13 below.)

12. BIOMASS FUEL FOR FOSSIL FUEL. Add 100 times the current Brazil or US ethanol production, with the use of 250 x 106 hectares (one-sixth of world cropland).

We endorse using some biomass (i.e. biodiesel) as a short term replacement for fossil fuels while new and better
carbon-free technologies are developed. We endorse this step as long as biofuels are made from waste, not crops, and don’t displace farmland or rainforests.

Creating a hydrogen* fuel cell infrastructure for transportation
and other uses—and then making hydrogen from coal is a non-starter. It increases the use of coal** for future energy needs, with no assurances that carbon capture will work—or that society will use it. The combined costs and energy-intensity of creating a hydrogen infrastructure far outweighs the costs of going to scale with wind and solar.

14. CAPTURE CO2 AT COAL-TO-SYNFUELS PLANTS. Introduce CCS at synfuels plants producing 30 million barrels a day from coal, if half of feedstock carbon is available for capture.

Developing synfuels is another non-starter. It increases the use of coal** for future energy needs, with no assurances that carbon capture will work or will be used. As is the case with creating a hydrogen infrastructure, the cost and energy intensity of developing the large-scale plants and systems for synfuels far outweighs the costs of going to scale with wind and solar.

15. NUCLEAR POWER FOR COAL POWER. Add 700 GW (twice the current capacity).

Increasing the use of nuclear power is a total non-starter. Waste, proliferation, terrorism, and accidents rule nuclear
out entirely. Lack of sites, increasing costs as more plants are built, the unwillingness of the private sector to insure nuclear, and the impossibility of building enough plants fast enough to meet the scale required in this wedge in the next ten years are more nails in nuclear power’s coffin.

*Hydrogen is not a source of energy. It must be generated by a power source such as solar or coal. Creating a hydrogen fuel cell system and then making hydrogen from coal-fired energy would be a climate nightmare.

**In addition to carbon emissions, the other enormous environmental and community health hazards from mining and burning coal also rule out expanding coal-based technologies.